A central problem for theories of memory development is how the superior memory of children and adults evolves from the memory abilities of infants and whether the mechanisms underlying this evolution are the same or different. The paucity of data on infant long-term memory precludes a current solution. In this application, research is proposed that will narrow the large gap between what is known about long-term memory in children and adults and what is known about short-term recognition memory in infants. Three questions fundamental to an understanding of infant memory development will be addressed: (1) How do selective attention, perception, and differences in information processing affect what is encoded and retrieved at different ages? (2) How do new experiences interact with and modify established memories, and what are the temporal constraints on such interactions at different ages? and (3) What are the consequences of retrieving active and inactive memories for the accessibility and organization of their different components? Answers will be achieved via an instrumental learning procedure previously used to study memory from 2-6 months and analogous procedures that will be developed for use at 9-12 months. In these procedures, infants learn a response that activates a distinctive toy in a distinctive context; 1 day later, their memory contents are probed with a retrieval cue. Infants indicate whether or not the information in the cue or context was encoded by whether or not they perform the learned response. The stable relation between effective retrieval cues after 1 day and effective memory primes after 2-3 weeks allows a convergent test of the results via a reminding procedure. This research will provide new information about normal memory development in infancy and its relation both to memory processes of children and adults and to neuropsychological research on brain mechanisms implicated in memory formation. From a health perspective, the research will provide a standard for detecting early cognitive deficits (or giftedness), particularly deficits that subsequently surface in tasks that require the utilization (retrieval) of accumulated, experienced-based information.